Room temperature vulcanizable compositions containing a diorganopolysiloxane having terminal condensable groups, a silicon compound having at least 3 Si-bonded hydrolyzable groups and an inorganic filler having a surface area of at least 50 m.sup.2 /g in which the surface of the inorganic filler contains organosilyl groups is described in U.S. Pat. No. 3,868,345 to Kratel et al. These compositions may be stored under anhydrous conditions, but when exposed to atmospheric moisture, vulcanize at room temperature to form elastomers.
Room temperature vulcanizable organopolysiloxane compositions having improved heat stability are described in U.S. Pat. No. 3,497,570 to Yerrick. These compositions, which are curable in the presence of moisture to form elastomers, contain acyloxy endblocked diorganopolysiloxanes and from 1.0 to 15.0 percent by weight based on the weight of the diorganopolysiloxanes of a polyacrylonitrile. Although, it is known that the heat stability of the resultant elastomers can be improved by the addition of a polyacrylonitrile, it has not been known heretofore that the adhesion of elastomers to a substrate upon which they are formed can be substantially improved by using the modified inorganic filler of this invention.
Thus, compared to the room temperature vulcanizable compositions known heretofore, the compositions of this invention have the advantage that the resultant elastomers exhibit better adhesion on the substrates upon which they have been cured and/or they provide better resistance to rupture.
Therefore, it is an object of this invention to provide a composition which may be stored under anhydrous conditions, but when exposed to atmospheric moisture, cures at room temperature to form an elastomer. Another object of this invention is to provide a room temperature vulcanizable composition containing a modified inorganic filler. Still another object of this invention is to provide a composition which is vulcanizable at room temperature to form an elastomer having improved adhesive properties. A further object of this invention is to provide a composition which when applied to a substrate and cured thereon exhibits improved adhesion to the substrate.